Overflow filter systems are typically used in salt water aquariums, but can also be used in fresh water aquariums. Conventional overflow systems have an overflow wall or barrier that extends continuously upward from the floor of an aquarium tank surrounding a filter intake region. Plumbing for a remote wet/dry filter system and a return pump is usually installed through the floor of the aquarium in the filter intake region. A filter intake and a return line for the wet/dry filter system are typically installed through the floor of the aquarium in the filter intake region. One of the main reasons overflow walls are used is to avoid flooding in the event that the wet/dry filter and/or pump system fails (e.g., because of loss of power to the pump, etc.).
In an overflow filter system, water in the main region of the aquarium tank flows over the top of the overflow wall into the filter intake region. The water in the filter intake region then flows by gravity through a pre-filter at the filter intake and downward out of the aquarium through a drain hole to the remote wet/dry filter. After being filtered in the wet/dry filter, the water is returned to the aquarium by a return pump. Although the return tube is typically installed through the floor of the aquarium in the filter intake region, the outlet spout for the return tube returns the filtered water to the main region of the aquarium tank outside of the filter intake region. Water thus circulates throughout the aquarium system as follows: 1) water from the main region of the aquarium tank flows over the overflow wall into the filter intake region; 2) water in the filter intake region flows through the pre-filter and falls by gravity through the drain hole to the remote wet/dry filter; and 3) filtered water from the wet/dry filter is pumped through a return line to the main region of the aquarium tank outside of the filter intake region.
In conventional overflow filter systems, the pulling action over the overflow wall draws water from the upper layers of the water in the main region of the aquarium tank. However, in most applications, drawing water from the lower layers in the main region of the aquarium tank, or from a combination of upper and lower layers in the main region of the aquarium tank, is desirable.